Field of the Disclosure
The present disclosure, for example, relates to wireless communication systems, and more particularly to techniques for handling feedback for downlink transmissions in a shared radio frequency spectrum band.
Description of Related Art
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UE). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
Some modes of communication may allow communication between a base station and a UE over a shared radio frequency spectrum band, or over different radio frequency spectrum bands (e.g., a dedicated radio frequency spectrum band and a shared radio frequency spectrum band) of a cellular network. With increasing data traffic in cellular networks that use a dedicated (e.g., licensed) radio frequency spectrum band, offloading of at least some data traffic to a shared radio frequency spectrum band may provide a cellular operator with opportunities for enhanced data transmission capacity. A shared radio frequency spectrum band may also provide service in areas where access to a dedicated radio frequency spectrum band is unavailable.
Prior to gaining access to, and communicating over, a shared radio frequency spectrum band, a base station or UE may perform a listen before talk (LBT) procedure to contend for access to the shared radio frequency spectrum band. An LBT procedure may include performing a clear channel assessment (CCA) procedure to determine whether a channel of the shared radio frequency spectrum band is available. When it is determined that the channel of the shared radio frequency spectrum band is available, a channel reservation signal (e.g., a channel usage beacon signal (CUBS)) may be transmitted to reserve the channel. If it is determined that the channel is not available, a CCA procedure may be performed for the channel again at a later time.